Validation of intensity-modulated radiotherapy commissioning as per recommendations in test plans of the American Association of Physicists in Medicine task group 119 report

Abstract

In the present study, intensity-modulated radiotherapy (IMRT) commissioning has been validated as per the task group report 119 (TG119) of the American Association of Physicists in Medicine (AAPM). The plans have been done on structure and computed tomography scanned data set downloaded from the AAPM website. IMRT test planning has been performed to achieve conformed dose and dose distribution similar to that described in the AAPM TG119 report. Point dose measurements with ionization chamber have been taken on solid water phantom at a depth of 7.5 cm. Measurements were performed in two locations, i.e. at target volume and low dose avoidance structure, with planned machine parameters. Gamma evaluation of dose distribution produced by each field has also been done individually using electronic portal imaging device (EPID). Overall mean deviation obtained for ion chamber measurement was −0.012 (standard deviation [SD]: 0.015) with confidence limit (CL) 0.043 and −0.0012 (SD: 0.009) with CL 0.020 in high-dose region and low-dose region, respectively. Overall mean gamma passing in portal dosimetry calculated specifically for EPID has been observed 99.5% with SD 0.33 and CL 1.13. The results obtained for ion chamber dosimetry and portal dosimetry are much better than those reported in the AAPM TG119 report. Better results in gamma evaluation further reduced CL for EPID users.